Can Permanganate Oxidizable Carbon Predict Soil Function Responses To Soil Organic Matter Management?

We evaluatedpermanganate oxidizable carbon (POXC) as a rapid test for identifying soils where improved organic matter management could improve soil function. At three sites, pairs of fields with similar soils but contrasting management history (cropped vs. sod) were studied. Fields historically in sod had higher initial total organic C (TOC) and POXC than historically cropped fields. Two cover crop treatments (rye and no cover) were applied within fields. We examined responses to rye treatment within management history for water stable aggregates (WSA), mineralizable C (C-min), mineralizable nitrogen (N-min)(,) and Year 2 POXC. Rye treatment had significant positive effects on C-min, N-min, WSA, and Year 2 POXC. Across all sites, historically cropped fields had significantly greater responses to rye in N-min, WSA, and Year 2 POXC. Every parameter showed a significantly greater response to rye in historically cropped fields within at least one site. Significant responses were negatively correlated to initial TOC and initial POXC, indicating greater responses where initial soil C tested lower. Initial TOC and POXC were similarly related to responses, but the POXC method is rapid and simple, requires less expensive equipment, and can be carried out in the field, making it a practical alternative, or complement, to TOC in soil health assessment. Use of POXC could facilitate identification of soils where improved soil organic matter management could sequester soil C and improve soil functioning.